The present invention relates, in general, to integrated circuits and, more particularly, to an integrated circuit for generating a bandgap reference voltage.
Electronic circuits such as, cellular telephones, laptop computers, coders/decoders, and voltage regulators require a stable and accurate reference voltage for effective operation. However, reference voltages may not remain constant due to temperature variations that occur during circuit operation. A circuit known as a bandgap reference voltage generator is used to compensate for the temperature dependence of reference voltages and provide a constant reference voltage.
Typically, a bandgap reference voltage generator must provide a reference voltage that has less than a one percent change in voltage over the operating temperature range. One indication of the performance of the reference voltage generator is the shape of the plot of the reference voltage versus temperature. The plot is characterized by the reference voltage increasing as the temperature is increased until an inflection temperature is reached, at which point the reference voltage decreases. The curvature of this plot is referred to as the characteristic bow of the temperature response.
A common technique for generating a bandgap reference voltage is to use thin film resistors to generate the reference voltage. Although thin film resistors have a temperature coefficient of about zero, they require additional processing steps that increases the cost of the integrated circuit.
Accordingly, it would be advantageous to have an improved method and circuit for providing a stable and accurate reference voltage. It would be of further advantage to compensate for second order effects on the temperature coefficient of a transistor's base-emitter voltage. In addition, it would be desirable to provide a low cost bandgap reference voltage generator that is independent of changes in operating and process characteristics.